Abstract Detail

The evolution of functional traits in plants: is the giant still sleeping?

Heyduk, Karolina [1], Berry, Kerrie [2], Daum, Chris [3], Lipzen, Anna [3], Grimwood, Jane [4], Jenkins, Jerry [5], Plott, Chris [5], Schmutz, Jeremy [5], Leebens-Mack, Jim [6].

New insights into the evolution of CAM photosynthesis from genomes of Yucca species.

About 8% of land plants use a modified form of photosynthesis known as Crassulacean acid metabolism (CAM), whereby they temporally separate acquisition of atmospheric CO₂ from fixation via Rubisco. CAM plants open their stomata at night, store incoming CO₂ temporarily in their cells, then move CO₂ into the chloroplasts during the day while stomata are closed to flood Rubisco with high amounts of carbon. This temporal separation means CAM plants lose less water through their stomata, as nighttime temperatures and relative humidity reduce the overall transpiration rate, and thus are able to live in environments ranging from seasonally dry to the extreme arid regions of the world. CAM has evolved independently at least 35 times, but our understanding of the genetics underlying its origins are hampered by a lack of systems with closely related C₃ and CAM taxa. Here we explore the genomic landscape of CAM in a newly emerging model for CAM evolution in the genus Yucca (Asparagaceae). Extensive physiological work has been done in Yucca aloifolia (CAM), Y. filamentosa (C₃), and a hybrid offspring Y. gloriosa (C₃+CAM). Previous transcriptomic analyses revealed stark contrasts between the two parental species in terms of gene expression, but surprisingly also highlighted a number of canonical CAM genes with shared expression, despite Y. filamentosa being a C₃ plant. To improve our understanding of both the changes that are needed at a genomic level for CAM to evolve, as well as a genetic pre-adaptation that may have facilitated the evolution of CAM, we generated draft genomes of both Y. aloifoia and Y. filamentosa, as well as whole-genome re-sequence and RNA-seq data for 24 individuals of the hybrid Y. gloriosa. With this new genomic data, we assess differences in gene copy number and expression in the parental species. We find that duplication of a key gene is associated with its recruitment for CAM photosynthesis in Y. aloifolia. Across genotypes of the hybrid, which segregate for the ability to use CAM under drought, we find differential expression of both CAM genes and circadian regulators. This powerful comparative Yucca system, combined with new genomic resources, provides a refined understanding of the genetics of CAM.

1 - Yale University, Department of Ecology and Evolutionary Biology, 165 Prospect Street, New Haven, CT, 06520, United States
2 - Joint Genome Institute, 2800 Mitchell Dr. #100, Walnut Creek, CA, 94598, USA
3 - Joint Genome Institute, 2800 Mitchell Dr. #100, Walnut Creek, CA, 94598, United States
4 - HudsonAlpha, 601 Genome Way Northwest, Huntsville, AL, 35806, USA
5 - HudsonAlpha, 601 Genome Way Northwest, Huntsville, AL, 35806, United States
6 - University Of Georgia, Plant Biology, 2101 Miller Plant Sciences, Athens, GA, 30602, United States

Keywords:
Whole Genome Sequencing
RNA sequencing
Physiology
photosynthesis
Gene duplication.

Presentation Type: Colloquium Presentations
Session: CO04, The Evolution of Functional Traits in Plant: Is the Giant Still Sleeping?
Location: Tucson J/Starr Pass
Date: Monday, July 29th, 2019
Time: 2:00 PM
Number: CO04003
Abstract ID:566
Candidate for Awards:Margaret Menzel Award